Patent Application
20080050654
Referring to
Cathode 16 includes a cathode current collector and a cathode material that is coated on at least one side of the cathode current collector. The cathode material includes one or more cathode active materials. In some embodiments, the cathode material can also include one or more conductive materials (e.g., conductive aids, charge control agents) and/or one or more binders.
Cathode 16 includes a relatively high loading of the cathode material. Typically, as the loading of the cathode material in cathode 16 increases, the electrochemical performance of cathode 16 can become enhanced. In certain embodiments, at least one side of the cathode current collector can have a loading of more than 21.5 milligrams (e.g., at least about 22 milligrams, at least about 23 milligrams, at least about 24 milligrams, at least about 25 milligrams, at least about 26 milligrams, at least about 27 milligrams, at least about 28 milligrams, at least about 29 milligrams, at least about 30 milligrams, at least about 31 milligrams, at least about 32 milligrams, at least about 33 milligrams, at least about 34 milligrams) and/or at most about 35 milligrams (e.g., at most about 34 milligrams, at most about 33 milligrams, at most about 32 milligrams, at most about 31 milligrams, at most about 30 milligrams, at most about 29 milligrams, at most about 28 milligrams, at most about 27 milligrams, at most about 26 milligrams, at most about 25 milligrams, at most about 24 milligrams, at most about 23 milligrams, at most about 22 milligrams) of the cathode material per square centimeter of the side of the cathode current collector. As used herein, the loading of cathode material on one side of cathode 16 is calculated by sampling of a coated area or, for example, when both sides are coated in the same manner, according to formula (1) below, in which Lcm=average loading of cathode material per side, Mcat=weight of the coated cathode, Mcc=weight of the cathode current collector, and Acc=coated area of the cathode current collector:
L
cm=(Mcat−Mcc)/2Acc (1)
where sample area for Lcm, Mcat and Acc is the same.
Examples of cathode active materials that can be included in the cathode material of cathode 16 include metal oxides, halides, chalcogenides, sulfur, organosulfur polymers, and conducting polymers. For example, in some embodiments, cathode 16 can include iron disulfide (FeS2). Other examples of cathode active materials include MnO2, V2O5, CoF3, MoS2, SOCl2, MoO3, S, (C6H5N)n, and (S3N2)n, where n is at least 2.
In some embodiments, the cathode material of cathode 16 can include a relatively high weight percent of iron disulfide. In certain embodiments, the cathode material of cathode 16 can include at least about 85 percent by weight (e.g., at least about 87 percent by weight, at least about 89 percent by weight, at least about 91 percent by weight) and/or at most about 99 percent by weight (e.g., at most about 92 percent by weight, at most about 91 percent by weight, at most about 89 percent by weight, at most 87 percent by weight) of iron disulfide. In some embodiments, a battery with a cathode including a cathode material having a relatively high weight percent of iron disulfide can exhibit enhanced electrochemical performance relative to a battery with a cathode including a cathode material having a relatively low weight percent of iron disulfide.
Examples of conductive materials include conductive aids and charge control agents. Specific examples of conductive materials include carbon black, graphitized carbon black, acetylene black, and graphite. The conductive materials can be used, for example, to enhance the electronic conductivity of cathode 16 within electrochemical cell 10. In some embodiments, the conductive materials can enhance the electronic conductivity of cathode 16 while also occupying a relatively low volume of cathode 16.
As the volume of cathode 16 that is occupied by conductive materials decreases, the volume of cathode 16 that is available for cathode active materials can increase. As the amount of cathode active material used in cathode 16 increases, the electrochemical performance of electrochemical cell 10 can also increase. In certain embodiments, the cathode material of cathode 16 can include at most about eight percent by weight (e.g., at most about seven percent by weight, at most about six percent by weight, at most about five percent by weight, at most about four percent by weight) and/or at least about three percent by weight (e.g., at least about four percent by weight, at least about five percent by weight, at least about six percent by weight, at least about seven percent by weight) of one or more conductive materials.
In some embodiments, the cathode material of cathode 16 can include at most about three percent by weight (e.g., at most about two percent by weight) and/or at least about one percent by weight (e.g., at least about two percent by weight) carbon black. In certain embodiments, the cathode material of cathode 16 can include at most about seven percent by weight (e.g., at most about six percent by weight, at most about five percent by weight, at most about four percent by weight, at most about three percent by weight) and/or at least about two percent by weight (e.g., at least about three percent by weight, at least about four percent by weight, at least about five percent by weight, at least about six percent by weight) graphite.
As discussed above, in some embodiments, the cathode material of cathode 16 can include one or more binders. The binders can help improve cohesion and adhesion of the cathode material and help keep the powders suspended in slurry. Examples of binders include linear di- and tri-block copolymers. In certain embodiments, the linear di- and tri-block copolymers can be substantially free of double bonds in their primary polymer chains, and/or can include conjugated double bonds in their primary polymer chains. In some embodiments, a binder can include polystyrene (e.g., in an amount of from 29 percent by weight to 33 percent by weight). Additional examples of binders include linear tri-block polymers cross-linked with melamine resin; ethylene-propylene copolymers (e.g., with an ethylene content of at least about 40 percent); ethylene-propylene-diene terpolymers (e.g., with ethylene contents below about 70 percent); tri-block fluorinated thermoplastics (e.g., TFE/HFP/VF2 terpolymer, in which TFE is tetrafluoroethylene, HFP is hexafluoropropylene, and VF2 is vinylidene fluoride); fluorinated polymers (e.g., polytetrafluoroethylene (PTFE)); hydrogenated nitrile rubber (e.g., with at least about 30 percent acrylonitrile); fluoro-ethylene-vinyl ether copolymers; thermoplastic polyurethanes (TPU); thermoplastic olefins (TPO); styrene-ethylene-butylene-styrene (SEBS) block copolymers (e.g., Kraton® G1651 polymer); and polyvinylidene fluoride (PVDF) homopolymers (e.g., Kynar® 761 polymer). In some embodiments, the cathode material of cathode 16 can include a binder that is formed of a film-forming polymer. As used herein, a film-forming polymer can be added to a solvent to form a solution, which can then be dried to form a film. In certain embodiments, one or more binders can be modified (e.g., to result in enhanced cathode properties). As an example, a low molecular weight rubber binder can be cross-linked and/or vulcanized. The presence of the cross-linked and/or vulcanized binder in a cathode can, for example, enhance the solvent resistance of the cathode. In some embodiments, a binder can be cross-linked in a dryer (e.g., during a process in which cathode slurry is dried while supported by a cathode current collector).
In certain embodiments, the cathode material of cathode 16 can include at least about one percent by weight (e.g., at least about two percent by weight, at least about three percent by weight, at least about four percent by weight) and/or at most about five percent by weight (e.g., at most about four percent by weight, at most about three percent by weight, at most about two percent by weight) of one or more binders.
The cathode current collector in cathode 16 can be formed of, for example, one or more metals and/or metal alloys. Examples of metals include titanium, nickel, and aluminum. Examples of metal alloys include aluminum alloys (e.g., 1N30, 1230) and stainless steel. A cathode current collector can be in the form of, for example, a foil or a grid. For example, in some embodiments, a cathode current collector can be in the form of an aluminum foil. In certain embodiments, a cathode current collector can be formed of a relatively thin foil. For example, a cathode current collector can be formed of a foil having a thickness of at most about 35 microns (e.g., at most about 30 microns, at most about 25 microns) and/or at least about 20 microns (e.g., at least about 25 microns, at least about 30 microns). As the thickness of the foil that is used for the cathode current collector decreases, the volume in the cathode that is available for cathode material can increase. In some embodiments, a cathode current collector can be formed of a foil having a temper of H18 or H19. In certain embodiments, one or more primers can be applied to a cathode current collector. In some embodiments, a pre-primed foil (e.g., from Lamart Corp., Clifton, N.J.) can be used to form a cathode current collector. In certain embodiments, a cathode current collector can be formed of an aluminum foil that has been primed with a water-based primer (e.g., Dag® EB 012 water-based primer, from Acheson Industries). A water-based primer can be applied to a foil using, for example, spray, gravure, and/or intermittent reverse roll coating techniques. In certain embodiments, a cathode current collector can include from about 0.5 milligram to about one milligram of one or more primers per square centimeter of the cathode current collector.
Cathode 16 can be formed in any of a number of different ways. In some embodiments, cathode 16 can be formed as follows.
First, one or more cathode active materials, conductive materials, and/or binders are combined with one or more solvents to form a slurry (e.g., by dispersing the cathode active materials, conductive materials, and/or binders in the solvents using a double planetary mixer). In some embodiments, the slurry can include at least about 55 percent by weight (e.g., at least about 60 percent by weight, at least about 65 percent by weight) and/or at most about 70 percent by weight (e.g., at most about 65 percent by weight, at most about 60 percent by weight) of one or more cathode active materials, such as iron disulfide. In certain embodiments, the slurry can include at least about four percent by weight (e.g., at least about five percent by weight) and/or at most about six percent by weight (e.g., at most about five percent by weight) of one or more conductive materials (e.g., carbon black, graphite). In some embodiments, the slurry can include at least about two percent by weight (e.g., at least about three percent by weight, at least about four percent by weight) and/or at most about five percent by weight (e.g., at most about four percent by weight, at most about three percent by weight) of one or more binders (e.g., PVDF homopolymer, SEBS copolymer).
As discussed above, the slurry includes one or more solvents, such as a blend of solvents. In some embodiments, the slurry can include one or more solvents having relatively low volatility (e.g., N-methyl-2-pyrrolidone (NMP)). In certain embodiments, a slurry including one or more of these solvents can be used to form a relatively thick coating on a cathode current collector, and/or to form a cathode that has a relatively low susceptibility to cracking. In some embodiments, a slurry including one or more of these solvents can be used to form a coating that has few or no defects, and/or that is relatively uniform. Examples of solvents include aromatic hydrocarbons (e.g., Shell Sol® A100) and aliphatic hydrocarbons (e.g., Shell Sol® OMS). In some embodiments, a slurry can include one or more normal hydrocarbons (e.g., hexane) and/or branched hydrocarbons.
In certain embodiments, the slurry can include one or more iso- and/or cyclo-paraffinic solvents (e.g., VM&P Naphtha HT®).
In some embodiments, the slurry can include at least about 25 percent by weight (e.g., at least about 30 percent by weight, at least about 35 percent by weight, at least about 40 percent by weight) and/or at most about 45 percent by weight (e.g., at most about 40 percent by weight, at most about 35 percent by weight, at most about 30 percent by weight) of one or more solvents.
In certain embodiments, the slurry can have a relatively high viscosity. In some embodiments, the slurry can have a viscosity of at least about 3,000 mPas (e.g., at least about 4,000 mPas, at least about 5,000 mPas, at least about 6,000 mPas, at least about 7,000 mPas, at least about 8,000 mPas, at least about 9,000 mPas, at least about 10,000 mPas, at least about 11,000 mPas, at least about 12,000 mPas, at least about 13,000 mPas, at least about 14,000 mPas) and/or at most about 40,000 mPs (e.g., at most about 14,000 mPas, at most about 13,000 mPas, at most about 12,000 mPas, at most about 11,000 mPas, at most about 10,000 mPas, at most about 9,000 mPas, at most about 8,000 mPas, at most about 7,000 mPas, at most about 6,000 mPas, at most about 5,000 mPas, at most about 4,000 mPas). For example, the slurry can have a viscosity of from about 3,000 mPas to about 6,000 mPas. As used herein, the viscosity of a slurry is measured using a Brookfield® viscometer (Model DV III, available from Brookfield Engineering Laboratories.
In certain embodiments, a slurry that is used to form a cathode can include from about 55 percent to about 70 percent by weight of iron disulfide, from about four percent to about six percent by weight of one or more conductive materials (e.g., carbon black, graphite), from about two percent to about five percent by weight of one or more binders (e.g., PVDF homopolymer, SEBS copolymer), and from about 25 percent to about 45 percent by weight of one or more solvents (e.g., Shell Sol® A100, Shell Sol® OMS, NMP). In some embodiments, a slurry that is used to form a cathode can include from about 55 percent to about 75 percent by weight solids, and can have a viscosity of from about 3,000 mPas to about 15,000 mPas (e.g., from about 3,000 mPas to about 6,000 mPas).
After the slurry has been formed, the cathode current collector (e.g., aluminum foil) can be coated with the slurry. In some embodiments, the coating process can include extrusion die coating or roll-coating.
In certain embodiments, an extrusion die coating process can include using a closed, pressurized fluid dispensing system. For example, as shown in
In some embodiments, roll-coating can be done using a knife-over-roll coating process. In certain embodiments, the roll coating process can be an intermittent or a continuous roll coating process.
Referring to
Separation of rolls 104 and 106 can also produce uncoated spaces between adjacent slurry patches. Separation of rolls 104 and 106 can be cam or computer controlled.
The coating speed is variable from one cathode to a different cathode. This can, for example, allow for the application of slurry coatings having varying viscosities. As an example, relatively viscous slurries can be applied to a continuous sheet using a relatively slow coating speed. In some embodiments, coating speed can be varied for a given continuous sheet. This can, for example, result in a cathode having non-uniform slurry patches on the sheet.
After first side 112 of continuous sheet 98 has been coated with slurry patches, the patches are dried by passing the sheet through multiple drying zones (e.g., three drying zones) in which heated air is directed at the wet surface. The air speed and temperature are gradually ramped up from zone to zone. The coated sheet can be dried, for example, for about 0.5 minutes to 15 minutes in each zone. In certain embodiments, a multi-zone dryer can include a zone having a temperature of about 40° C., a zone having a temperature of about 60° C., and a zone having a temperature of about 130° C. The coated sheet can pass through the drying zones at a line speed, for example, of at least about 0.5 meter per minute (e.g., at least 0.7 meter per minute) and/or at most 0.8 meter per minute.
The coating and drying processes described above optionally can be repeated on second side 114 of continuous sheet 98 (
A same or analogous drying procedure can be used in conjunction with other coating processes, for example, extrusion die coating.
In some embodiments, the coating process can include a reverse roll-coating process. A reverse roll-coating process is described, for example, in Stevanovic, U.S. patent application Ser. No. 11/313,509, filed on Dec. 21, 2005, and entitled “Cathode for Battery”.
In certain embodiments, the coating speed for any of the coating procedures can be at least about 0.2 meter per minute (e.g., at least about 0.6 meter per minute, at least about 0.7 meter per minute, at least about 0.8 meter per minute, at least about 0.9 minute) and/or at most about one meter per minute (at most 0.9 meter per minute, at most 0.8 meter per minute, at most 0.7 meter per minute, at most 0.6 meter per minute). For example, the coating speed can be from about 0.5 meter per minute to about 0.7 meter per minute.
In certain embodiments, a cathode that has been dried can include from about 85 percent by weight to about 92 percent by weight of iron disulfide, less than about five percent by weight of one or more binders, and from about three percent to about seven percent by weight of one or more conductive materials.
After a cathode has been dried, the cathode can be calendered. Before calendering, the uncoated edges of the cathode are slit off to limit wrinkling of the coating-free zones. The cathode can be calendered using a four-roll modified “Z” calender with a roll width of about 300 mm inches and a roll diameter of about 400 mm. The calender rolls can be heated and/or cooled as needed. In some embodiments, the cathode can be calendered off-line, in a continuous mode (e.g., reel-to-reel). In certain embodiments, a 2×2 roll configuration with two nips, or a two-roll configuration with one nip, can be used. In certain embodiments, calendering can occur at a temperature of at least about 25° C. and/or at most about 60° C. In some embodiments, the calender can have a line speed of at least about 0.9 meter per minute (e.g., at least about one meter per minute, at least about 1.1 meters per minute) and/or at most about 1.2 meters per minute (e.g., at most about 1.1 meters per minute, at most about one meter per minute). In some embodiments, elongation of a foil current collector (e.g., a 20-micron thick current collector) after calendering can be less than 1.5 percent. In certain embodiments, a foil current collector can be relatively unlikely to experience strain-hardening as a result of the calendering process.
In some embodiments, the calendered cathode can have a thickness of at least about 0.15 millimeter (e.g., at least about 0.175 millimeter, at least about 0.18 millimeter, at least about 0.19 millimeter, at least about 0.2 millimeter, at least about 0.225 millimeter, at least about 0.25 millimeter, at least about 0.275 millimeter) and/or at most about 0.3 millimeter (e.g., at most about 0.275 millimeter, at most about 0.25 millimeter, at most about 0.225 millimeter, at most about 0.2 millimeter, at most about 0.19 millimeter, at most about 0.18 millimeter, at most about 0.175 millimeter). For example, in some embodiments, the cathode can have a thickness of at least 0.172 millimeter and/or at most 0.188 millimeter.
In certain embodiments, calendering can result in the reduction of pores in the cathode material of a cathode. These pores can, for example, permit an electrolyte to diffuse within a battery including the cathode. The diffusion of the electrolyte can, in turn, result in enhanced electrochemical performance of the battery. In some embodiments, the cathode material of a cathode can have a porosity of at least about 20 percent (e.g., at least about 25 percent, at least about 30 percent) and/or at most about 35 percent (e.g., at most about 30 percent, at most about 25 percent). In certain embodiments, the cathode material of a cathode can have a porosity of from about 22 percent to about 30 percent. As used herein, the porosity of the cathode material of a cathode is equal to the percent by volume of the cathode material that is occupied by pores. The porosity of the cathode material is calculated according to equation (2) below, in which Vfinal=volume of the final cathode, and Vtheo=theoretical volume of the cathode material in the final cathode minus the volume of the current collector:
In some embodiments, calendering can result in the formation of a relatively thin cathode. As one or more of the dimensions (e.g., thickness) of a cathode decreases, the amount of space that is available within a battery including the cathode can increase. This space can be used, for example, to hold other battery components and/or to accommodate gas evolution during battery operation. In certain embodiments, after a cathode has been calendered, the cathode can have a thickness that is at most about 85 percent (e.g., at most about 82 percent, at most about 80 percent, at most about 78 percent) and/or at least about 75 percent (e.g., at least about 78 percent, at least about 80 percent, at least about 82 percent) of the thickness of the cathode prior to calendering.
Anode 12 includes one or more anode active materials, usually in the form of an alkali metal (e.g., lithium, sodium, potassium) and/or an alkaline earth metal (e.g., calcium, magnesium). Anode 12 can include an alloy of an alkali metal (e.g., lithium) and an alkaline earth metal and/or an alloy of an alkali metal and aluminum. For example, in some embodiments, anode 12 can include a lithium-aluminum alloy. Alternatively or additionally, anode 12 can include a lithium-insertion compound (e.g., such as LiC6, Li4Ti5O12, LiTiS2). Anode 12 may include a substrate (e.g., a current collector), or may not include a substrate. In some embodiments, particularly anode 12 can include one or more binders. Examples of binders include polyethylene, polypropylene, styrene-butadiene rubbers, and polyvinylidene fluoride (PVDF). In some embodiments in which anode 12 includes one or more binders, the anode active materials can include tin-based materials, carbon-based materials (e.g., carbon, graphite, an acetylenic mesophase carbon, coke), metal oxides, and/or lithiated metal oxides. The anode active material and one or more binders can be mixed to form a paste which can be applied to a substrate. Specific anode active materials that are used in a cell may be a function of, for example, the type of cell (such as primary or secondary).
The electrolytic solution or electrolyte can be in liquid, solid or gel (polymer) form. In some embodiments, the electrolyte can include an organic solvent such as propylene carbonate (PC), ethylene carbonate (EC), dimethoxyethane (DME) (e.g., 1,2-dimethoxyethane), butylene carbonate (BC), dioxolane (DX), tetrahydrofuran (THF), gamma-butyrolactone, diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), dimethylsulfoxide (DMSO), methyl formiate (MF), sulfolane, or a combination (e.g., a mixture) thereof. In certain embodiments, the electrolyte can include an inorganic solvent, such as SO2 or SOCl2. In some embodiments, the electrolyte can include one or more salts (e.g., two salts, three salts, four salts). Examples of salts include lithium salts, such as lithium trifluoromethanesulfonate (LiTFS), lithium trifluoromethane-sulfonimide (LiTFSI), and lithium hexafluorophosphate (LiPF6). Additional lithium salts that can be included are described, for example, in Suzuki, U.S. Pat. No. 5,595,841. Other salts that can be included in the electrolyte are bis(oxalato)borate salts. Bis(oxalato)borate salts are described, for example, in Totir et al., U.S. Patent Application Publication No. US 2005/0202320 A1, published on Sep. 15, 2005, and entitled “Non-Aqueous Electrochemical Cells”.
Positive lead 18 can include stainless steel, aluminum, an aluminum alloy, nickel, titanium, or steel. Positive lead 18 can be annular in shape, and can be arranged coaxially with the cylinder of a cylindrical cell. Positive lead 18 can also include radial extensions in the direction of cathode 16 that can engage the current collector. An extension can be round (e.g., circular or oval), rectangular, triangular or another shape. Positive lead 18 can include extensions having different shapes. Positive lead 18 and the current collector are in electrical contact. Electrical contact between positive lead 18 and the current collector can be achieved by mechanical contact. In some embodiments, positive lead 18 and the current collector can be welded together.
Separator 20 can be formed of any of the standard separator materials used in electrochemical cells. For example, separator 20 can be formed of polypropylene (e.g., nonwoven polypropylene, microporous polypropylene), polyethylene, and/or a polysulfone. Separators are described, for example, in Blasi et al., U.S. Pat. No. 5,176,968.
Case 22 can be made of, for example, one or more metals (e.g., aluminum, aluminum alloys, nickel, nickel plated steel, stainless steel) and/or plastics (e.g., polyvinyl chloride, polypropylene, polysulfone, ABS, polyamide).
Cap 24 can be made of, for example, aluminum, nickel, titanium, or steel.
While electrochemical cell 10 in
To assemble the cell, separator 20 can be cut into pieces of a similar size as anode 12 and cathode 16 and placed therebetween, as shown in
Other configurations of an electrochemical cell can also be used, including, for example, the button or coin cell configuration, the prismatic cell configuration, the rigid laminar cell configuration, and the flexible pouch, envelope or bag cell configuration. Furthermore, an electrochemical cell can have any of a number of different voltages (e.g., 1.5 V, 3.0 V, 4.0 V). Electrochemical cells are described, for example, in Berkowitz et al., U.S. patent application Ser. No. 10/675,512, filed on Sep. 30, 2003, and entitled “Batteries”; Berkowitz et al., U.S. Patent Application Publication No. US 2005/0112467 A1, published on May 26, 2005, and entitled “Battery Including Aluminum Component”; and Totir et al., U.S. Patent Application Publication No. 2005/0202320 A1, published on Sep. 15, 2005, and entitled “Non-Aqueous Electrochemical Cells”, all of which are incorporated herein by reference.
The following examples are meant to be illustrative and not to be limiting.
Approximately 30 to 50 cathodes were made in Examples 1 and 2.
A cathode was prepared according to the following process.
First, 1.64 grams of Kraton® G1651 polymer, 66.15 grams of FeS2, 1.05 gram of carbon black (SOLTEX AB55), and 2.86 grams of graphite powder (TIMREX KS6) were dispersed in a mixture of 11.32 grams of Shell Sol® A100 and 16.98 grams of Shell Sol® OMS using a double planetary mixer to form a slurry. The slurry had a viscosity of 37000 mPas, which was determined using a Brookfield® viscometer DV III (spindle #7, 50 RPM).
Then, the slurry was coated onto both sides of a current collector formed of a 35-micron thick, temper H18 foil of aluminum alloy 1N30. The slurry was coated onto the current collector in two passes (one pass per side) using an extrusion die technique, at a speed of 0.3 meters per minute., and a gap setting of 225 microns.
Next, the slurry was dried by passing the slurry through a dryer having two zones, each zone 1.2 m long. The temperature in the first was 35° C., and in the second zone 70° C. The dry thickness of the coated cathode was 0.315 millimeters.
Finally, the cathode that resulted from the coating and drying process was calendered at a line speed of 0.9 meters per minute to a final thickness of 0.244 millimeters. After calendering, the cathode included porosity of about 24 percent of the volume of the cathode material.
After the cathode had been calendered, the cathode included 32.5 milligrams of cathode material per square centimeter per cathode side.
A cathode was prepared according to the following process.
First, 2.3 grams of Kynar® 761 polymer, 58.7 grams of FeS2, 0.9 gram of carbon black (SOLTEX AB55), and 2.6 grams of graphite powder (TIMREX MX-15) were dispersed in a mixture of 35.5 grams of N-methyl-2-pyrrolidone using a double planetary mixer to form a slurry. The slurry had a viscosity of 10000 mPas, which was determined using a Brookfield® DV II viscometer. (spindle #7, 50 RPM)
Then, the slurry was coated onto both sides of a current collector formed of a 35-micron thick, temper H18 foil of aluminum alloy 1N30. The slurry was coated onto the current collector in two passes (one pass per side) using an extrusion die technique, at a speed of 0.26 meters per minute, and a gap setting of 254 micron.
Next, the slurry was dried by passing the slurry through a dryer having two zones. Each zone 1.2 m long. The temperature in the first was 75° C., and in the second zone 100° C. The dry thickness of the coated cathode was 0.358 millimeters.
While certain embodiments have been described, other embodiments are possible.
As an example, while cathodes with PVDF homopolymer and/or SEBS copolymer binders have been described, in some embodiments, a cathode can alternatively or additionally include one or more other binders. Examples of binders include polytetrafluoroethylene (PTFE), ethylene-propylene copolymers, hydrogenated nitrile rubber, fluoro-ethylene-vinyl ether copolymers, thermoplastic polyurethanes, and thermoplastic olefins.
As an additional example, in some embodiments, a cathode can be wound (e.g., around a mandrel).
An alternative battery arrangement is disclosed in Berkowitz et al., U.S. Ser. No. ______/______ which is being filed on the same day as the parent application.
All references, such as patent applications, publications, and patents, referred to herein are incorporated by reference in their entirety.
Other embodiments are in the claims.
